JP3232027B2 - ATM communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ATM (Asynchronou).
s Transfer Mode) Used for communication. The present invention provides a plurality of A
Local area network by TM (hereinafter referred to as LAN)
It is suitable for use in large-scale ATM communication networks including In particular, the present invention relates to a traffic control technique in communication between LANs by ATM.

[0002]

2. Description of the Related Art In an ATM communication network, a large-scale ATM communication network is constructed by interconnecting LANs using a plurality of ATMs. This conventional example is shown in FIG.
This will be described with reference to FIG. FIG. 10 is a diagram showing a conventional ATM communication network.

In a conventional ATM communication network, for example, LAN
When the communication terminal 10 connected to 2-1 transfers a cell to the communication terminal 20, first, the communication terminal 20 as a destination is searched for in the LAN 2-1 and it is determined that the communication terminal 20 does not exist in the LAN 2-1. Is recognized, then LA
The cell is transferred to N2-2. Here, the communication terminal 20 as the destination is searched, and if it is recognized that the communication terminal 20 does not exist on the LAN 2-2, the cell is transferred to the LAN 2-3. By repeating such a procedure, the cell finally arrives at the communication terminal 20 connected to the LAN 2-4. If such a flow of cells occurs constantly, it is dealt with by providing a dedicated line 30.

[0004] In addition, the bridges 40 to 42 connecting the LANs 2-1 to 2-4 are connected to the cells that frequently pass through the bridges 40 to 42. Since it is possible to learn whether or not the cell exists, the cell transfer can be performed smoothly.

[0005]

SUMMARY OF THE INVENTION Such a conventional AT
In the M communication network, as the scale of the LANs 2-1 to 2-4 increases, the amount of traffic passing through the bridges 40 to 42 also increases.

For this purpose, it is necessary to provide a dedicated line 30 or to increase the line capacity of the bridges 40 to 42.
If the size of the is large, it will not be able to cope.

Further, the traffic distribution of the bridges 40 to 42 is not always distributed to the respective bridges 40 to 42 on average. -3, the traffic is biased in order from the bridge 42 closer to the LAN 2-4 to the bridge 41 and the bridge 40. Therefore, the capacity of each of the bridges 40-42 must be able to cope with the maximum traffic that can occur in the entire ATM communication network.

As described above, in the conventional ATM communication network, it is difficult to flexibly cope with traffic expected to increase in the future.

The present invention has been made in view of such a background, and an object of the present invention is to provide an ATM communication network which can flexibly cope with an increase in traffic. SUMMARY OF THE INVENTION An object of the present invention is to provide an ATM communication network capable of easily configuring a large-scale and large-capacity network. According to the present invention, A which can effectively use network resources
It is intended to provide a TM communication network.

[0010]

SUMMARY OF THE INVENTION The present invention is an ATM communication network comprising a plurality of LANs by ATM and a center network for transferring cells between the plurality of LANs. A feature of the present invention is that it comprises means for converting a cell coming from the LAN into an optical cell of an optical wavelength determined according to its destination and transferring it to the center network. There is provided an optical wavelength routing means in which the output path of the optical cell is set according to the wavelength of the optical cell. In the center network, it is preferable that an output route of the optical cell is fixedly set.

As a result, each LAN is connected to the center network in a star configuration, and it is possible to avoid a decrease in throughput due to the passage of traffic. The most important feature of the present invention is to realize an ATM communication network which does not require a complicated device such as a center server by using an optical wavelength routing means for the center network. Therefore, as compared to the case where a complicated device such as a center server is provided, the maintenance and inspection of the center network is not troublesome, and the probability of occurrence of a failure or the like is low.

The cell may be an optical cell already at the LAN stage, or may be an electric signal cell at the LAN stage and converted into an optical cell by the transfer means.

The transfer means includes a destination LAN.
It is preferable to include a table in which information on optical wavelengths to be transferred to the LAN is recorded.

Each LAN is provided with its own LA.
When an optical cell destined for a LAN other than N arrives, there is provided a means for converting the optical cell to a route other than the route from which the optical cell has arrived, converting the wavelength into the wavelength of the route, and returning the route. It is desirable.

Thus, even if a cell arrives at the LAN which cannot be directly transferred from the own LAN, the cell arrives at another L.
By transferring to the AN for the time being, this cell can finally reach the desired LAN.

By transferring in this manner, for example,
Even when traffic is concentrated between specific LANs, since the paths of optical cells are distributed throughout the center network, it is necessary to take measures such as specially increasing the transmission capacity of the paths between specific LANs as described above. However, network resources can be used effectively.

The return transfer means selects a wavelength addressed to the LAN having the shortest path from the own LAN among the LANs which the own LAN can directly transfer, converts the optical cell to the wavelength, and transfers the return. May be configured to include means for transmitting data directly to the local LAN.
In the AN, there is provided a means for selecting a wavelength destined to the LAN having the shortest route to the LAN to which the optical cell is directed, converting the optical cell to the wavelength, and returning the wavelength. Is also good.

When the transfer destination is the LAN that has the shortest path from the own LAN, the fixed LAN is the transfer destination, so there is no need to change the transfer destination according to the destination of the optical cell. In addition, the control can be simplified without requiring any judgment in the control process. When the transfer destination is a LAN that has the shortest route to the LAN to which the optical cell is the destination, the transfer destination changes according to the destination of the optical cell. Can reach the desired destination in the shortest time. It is preferable to select the most appropriate method according to the state of the network.

Each of the LANs is provided with its own LA.
When an optical cell destined for a LAN other than N arrives, a plurality of copies of the optical cell are made, and the optical cell is assigned to a plurality of routes other than the route from which the optical cell arrives, to the wavelengths of the route. It is also possible to adopt a configuration including means for converting the data and returning the converted data.

According to this, no judgment is required in the control process, and the time for the optical cell to reach the desired destination can be minimized.

It is preferable that the loop-back transfer means include means for temporarily holding information on a route from which the optical cell has arrived, and means for allocating an optical wavelength for loop-forward transfer to the optical cell.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention. FIG. 2 is a diagram showing a table of the access control unit.

The present invention relates to a LAN 2-1 to ATM-2 based on ATM.
This is an ATM communication network provided with a center network 50 for transferring cells between the LANs 2-1 to 2-4.

Here, the feature of the present invention is that L
The cells arriving from the ANs 2-1 to 2-4 are converted into optical cells of an optical wavelength determined according to the destination, and the center network 50
Access control units 1-1 to 1-
The center network 50 includes optical wavelength routing units 3-1 to 3-1 as optical wavelength routing means in which the output route of the optical cell is set according to the wavelength of the input optical cell.
3-4. In this center network 50, the output route of the optical cell is fixedly set.

The access control units 1-1 to 1-4 include FIG.
As shown in FIG. 7, the table includes a table in which destination LANs 2-1 to 2-4 and optical wavelength information to be transferred to the LANs 2-1 to 2-4 are recorded.

In the access control units 1-1 to 1-4 and the center network 50, transfer by optical cells is performed. In the embodiment of the present invention, the LANs 2-1 to 2-4 are used as optical LANs for handling optical cells.
However, the LANs 2-1 to 2-4 may use electric signal cells and convert them into optical cells in the access control units 1-1 to 1-4.

[0027]

【Example】

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 and 2 are as described above. FIG. 3 is a diagram showing a method of transferring an optical cell according to the first embodiment of the present invention. FIG. 4 is a block diagram of the access control unit according to the first embodiment of the present invention.

The transfer of the optical cell between the LANs 2-1 to 2-4 is processed by the access control units 1-1 to 1-4 arranged in the LANs 2-1 to 2-4, respectively. For example, L
The transfer of the optical cell from the AN 2-1 to the LAN 2-2 is automatically transferred to the LAN 2-2 via the access control unit 1-2 by selecting the wavelength λ1 by the access control unit 1-1.

The center network 50 is a passive network, and the transfer is fixedly determined. However, it is possible to rearrange the configuration of the network instead of real-time depending on the traffic volume and the situation.

As shown in FIG. 2, the access control unit 2-i (i = 1 to 4) on the transmission side determines the destination LAN 1-j (j = 1 to 4) from the destination information of the optical cell. Or
However, j ≠ i) can be determined, and the cell can be transferred to the destination LAN 1-j by selecting the corresponding wavelength. (Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. FIGS. 3 and 4 are diagrams showing a method of transferring an optical cell according to the second embodiment of the present invention. In this example, LAN
There is no direct wavelength path from 2-1 to LAN 2-4. In that case, in the example shown in FIG. 3, the optical cell is transferred to the LAN 2-3 using the wavelength λ2. In the LAN 2-3, since the optical cell is not a destination in the LAN 2-3,
Again, this optical cell is transferred to the center network 50 using the wavelength λ3. The optical cell having the wavelength λ3 is transferred to the LAN 2-2 via the access control unit 1-2. In LAN2-2, wavelength λ
2, the optical cell can be transferred to the LAN 2-4, so that the optical cell can be transmitted to the target LAN 2-4.

In the example of FIG. 4, L is calculated using the wavelength λ1.
The optical cell is transferred to AN2-2. In the LAN 2-2, since the optical cell is not a destination in the LAN 2-2, the optical cell is transferred to the center network 50 again using the wavelength λ2.
In this way, this optical cell can be received by the target LAN 2-4.

As described above, when a desired wavelength path does not exist in the center network 50, cells are transferred to an adjacent LAN at random. Third Embodiment A third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram of an access control unit according to the third embodiment of the present invention. The access control unit 1 includes an arrival table 4 and holds a history of received cells for a certain period of time.
This holding time is set by the timer 8. As described in the second embodiment of the present invention, the controller 5 refers to the arrival table 4 at least when the optical cell having no destination in the LAN 2-i to which it is connected is transferred to the center network 50 again. Avoid transferring to the route you arrived. This makes it possible to avoid an infinite loop. At this time, the wavelength allocating unit 7 converts the wavelength of the optical cell into a wavelength suitable for the wavelength path for transferring the optical cell. The table shown in FIG. 2 is provided in the wavelength assignment unit 7. (Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of an access control unit according to the fourth embodiment of the present invention. In the access control unit 1, when an optical cell having no destination arrives in the LAN 2-i to which the access control unit 1 is connected, the cell is copied by the cell copying unit 6, and the optical cell is marked as a copy. The copied optical cells are converted into wavelengths suitable for the respective wavelength paths by the wavelength allocating section 7 and transmitted to all the wavelength paths that can be transferred from the access control section 1.

Thus, the optical cell transmitted to any one of the wavelength paths can be transmitted to the desired LAN 2 via the shortest wavelength path.
−j can be reached. At this time, an optical cell transferred to a wavelength path that reaches a dead end with respect to a desired destination has a rule that can be discarded at the destination. Since the mark which is the copied optical path is given, other original optical cells are not erroneously discarded. When one optical cell reaches a desired destination, another copied cell is discarded upon arrival.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram for explaining a method of transferring an optical cell according to the fifth embodiment of the present invention. In the first to third embodiments of the present invention, when an optical cell having no destination arrives at the access control unit 1-i (i = 1 to n) in the LAN 2-i to which the access control unit 1-i is connected. For the time being, a transfer method for delivering this optical path to a desired destination by transferring the optical cell to a wavelength path other than the wavelength path from which the optical cell has arrived has been described, but in the fifth embodiment of the present invention, At this time, L to which the optical cell is to be transferred for the time being.
AN2-k (any one of k = 1 to n, where k ≠ i) is determined in advance.

At this time, the LAN 2-k is set so that the distance of the wavelength path from the LAN 2-i to which the LAN 2-k is connected is the shortest. Accordingly, there is no need to make a determination in the process of controlling the transfer of the optical path, and the control can be simplified. In FIG. 7, k = 2.

(Sixth Embodiment) A sixth embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a diagram showing a display example of a LAN address. FIG. 9 is a diagram for explaining a method of transferring an optical cell according to the sixth embodiment of the present invention. As shown in FIG. 8, a plurality of upper bits of an optical cell are used as a LAN address. For example, in LAN2-1, the upper bits are always "# 1", and similarly, in LAN2-2, "# 2",
"# 3" for LAN2-3, "# 4" for LAN2-4
Becomes

In the sixth embodiment of the present invention, the access control unit 1
If an optical cell having no destination arrives in the LAN 2-i to which it is connected, a LAN 2-j (j = 1 to n) which is the destination of the optical cell is transmitted as much as possible. Where the distance of the wavelength path to j ≠ i) becomes shorter.
This optical cell is transferred to N2-k.

At this time, the controller 5-1 of the access control unit 1-i recognizes the destination of the optical cell by referring to the above-mentioned upper bits, and the LAN 2-i connected to itself closest to the destination is determined. LAN2 with direct wavelength path
-K transfer this optical cell.

As a result, when compared with the transfer method described in the fifth embodiment of the present invention, judgment is required in the control process, so that the control is inferior to the fifth embodiment in terms of simplification of control. Since the optical path can reach a desired destination without passing through a useless wavelength path, it is superior to the fifth embodiment of the present invention from the viewpoint of effective use of network resources.

[0040]

As described above, according to the present invention,
It is possible to flexibly cope with an increase in traffic. In addition, a large-scale and large-capacity network can be easily configured, and network resources can be effectively used.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a table of an access control unit.

FIG. 3 is a diagram showing a method of transferring an optical cell according to the first embodiment of the present invention.

FIG. 4 is a block diagram of an access control unit according to the first embodiment of the present invention.

FIG. 5 is a block diagram of an access control unit according to a third embodiment of the present invention.

FIG. 6 is a block diagram of an access control unit according to a fourth embodiment of the present invention.

FIG. 7 is a diagram for explaining an optical cell transfer method according to a fifth embodiment of the present invention.

FIG. 8 is a view showing a display example of a LAN address.

FIG. 9 is a diagram illustrating a method of transferring an optical cell according to a sixth embodiment of the present invention.

FIG. 10 is a diagram showing a conventional ATM communication network.

[Explanation of symbols]

 1, 1-1 to 1-4 Access control unit 2-1 to 2-4 LAN 3-1 to 3-4 Optical wavelength routing unit 4 Arrival table 5 Controller 6 Cell copying unit 7 Wavelength allocating unit 8 Timer 10, 20 Communication Terminal 30 Dedicated line 40-42 Bridge 50 Center network

Continuation of the front page (56) References JP-A-3-214837 (JP, A) 1997 IEICE General Conference B-6-24 (March 6, 1997) Acampor a, et al. , "TERABIT LIGHTWAVE NETWORK S: THE MULTIHOP APP ROACH", AT & T TECHNI CAL JOURNAL, VOLUME 66, ISSUE 6, pp. 21-34, NOVEMBER / DECEMBER 1987 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/56 H04L 12/46 H04L 12/66 H04B 10/20

Claims (5)

(57) [Claims] 1. A plurality of local area networks by ATM
And transfer cells between the multiple local area networks
An ATM communication network having a center network that performs communication, wherein a cell arriving from the local area network is used as its destination.
Therefore, the light is converted into an optical cell having a predetermined light wavelength, and
Means for transferring data within the network,This transfer means includes the destination local area network.
And optical wavelength information to be transferred to this local area network
And a table recorded with  The center network according to the wavelength of the input optical cell
The output path of the optical cell isFixedlySet optical wavelength loop
An ATM communication network, comprising: 2. The method according to claim 1, wherein each of said local area networks is provided separately.
Local area other than the local area network
When an optical cell destined for the network arrives, this optical cell
The local area other than the route where this optical cell arrived
In the local area network to which the network can directly transfer,
Local area with the shortest route from the local area network
A) Select the wavelength addressed to the network and convert the optical cell to that wavelength
2. The AT according to claim 1, further comprising:
M communication network. 3. The method according to claim 2, wherein the loop-back transfer means includes a local
In the local area network where the local area network can directly transfer
For the local area network addressed by the optical cell.
The wavelength addressed to the local area network with the shortest route
Select and convert the optical cell to that wavelength and forward it back
3. The ATM communication network according to claim 2 , further comprising : 4. Each of said local area networks is provided with
Local area other than the local area network
When an optical cell destined for the network arrives, this optical cell
Make multiple copies of this optical cell and this optical cell arrives
ATM network of claim 1, further comprising means for loopback transfer each respectively converted to route other than the plurality of routes for the wavelength of the route. Wherein said means for folding transfer claim and means for temporarily holding information of the route that the optical cell has arrived, and means for assigning a light wavelength for loopback transfer to the optical cell 2 Or the ATM communication network according to 4.